Marine Ecology


The EV Seminar takes place every Wednesday from 4.00 - 5.30  pm

Lecture hall

Announcement invited Speakers:


18 February, 2015

Ludewijk van Walraven, Royal Netherland Institute for Sea Research NIOZ


The invasive ctenophore Mnemiopsis leidyi in coastal waters of the Netherlands


In 2006 the comb jellyfish Mnemiopsis leidyi was observed in Dutch coastal waters for the first time, and in the years following was often seen by SCUBA divers in large densities in the Eastern Scheldt and Lake Grevelingen. This prompted a series of investigations aimed at qualifying and quantifying the spread of M. leidyi in the North Sea, Wadden Sea and estuaries of Zeeland. In this seminar I will give an overview of the results obtained in these studies, performed within the projects MEMO and GELMESOZOOPLANKTON. M. leidyi is present in large densities in most inshore coastal waters, and a modeling study suggests that the Dutch estuaries are an important source area for M. leidyi.  Its presence in brackish areas such as the Noordzeekanaal suggests it has adapted to lower salinity levels, which we investigated in a common garden experiment where we collected M. leidyi ctenophores in 8 and 31 PSU waters in the Noordzeekanaal and Wadden Sea, respectively. These were cultured and adapted to both salinity levels, measuring their growth and reproduction. Several differences were observed; mortality was much higher in the 8 PSU treatment in both groups and growth patterns differed between the different salinity treatments but not between groups. The egg production of ctenophores collected in the Noordzeekanaal area was significantly higher than that of the ones collected in the Wadden Sea, suggesting that they have adapted to spawning at lower salinities. Plans to re-salinise several freshwater bodies in the Netherlands are likely to increase available habitat for M. leidyi.













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Head of the Research Unit:

Prof. Dr. Thorsten Reusch
GEOMAR | Helmholtz Centre for Ocean Research Kiel
West shore Campus
Düsternbrooker Weg 20 
D-24105 Kiel 
Phone: +49-431 600-4550
Fax: +49-431 600-4553
e-mail: treusch(at)

Personal Assistant / Office Management:

Cornelia Rüther
Phone: +49-431 600-4551
e-mail: cruether(at)


Academic Theses